1. Technical Field
The present invention relates to radio systems and, more specifically, to radio systems adapted to operate at a minimum effective power transmission level. The invention also relates to methods of controlling the transmitted power of a radio signal.
In order to provide maximum security against reception of a transmitted signal by an unauthorised third party, it is desirable to use the lowest possible transmission power that enables effective reception to be achieved at the desired receiving station. During a normal radio transmission there may occur transient losses in signal strength which are known as "fading". Such fading may arise from cancellation of one incoming wave with another which has travelled from the transmitting radio by a different path. Therefore it is not sufficient merely to set the transmitted power level at a suitable minimum value, as any fading during transmission will cause errors at the receiving station.